De Tempo limite de CIFS e SMB no Windows
Idle Connection Timer
This is the amount of time that a connection can be idle before being disconnected. An idle connection is defined as a connection which has no existing open handles (no open files, directories, search contexts, etc.), and no pending operation. The Idle Connection Timer is implementation-specific. When the server receives a message, Server.Connection.IdleTime is set to the current time plus Server.AutoDisconnectTimeout [MS-CIFS].
On Windows servers it can be configured through the Autodisconnect registry key [KB297684]. \HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\ Value type: Dword Value name: Autodisconnect Default: 15 (minutes)
The Autodisconnect can also be configured through group policy: Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options “Microsoft network server: Amount of idle time required before suspending session”
Talvez a atualização tenha alterado ou redefinido um desses parâmetros.
Sugiro que você primeiro tente usar a Diretiva de Grupo e, se isso falhar, edite diretamente o Registro.